The present invention relates to a method of controlling a wavelength of a semiconductor laser applied to a WDM (wavelength division multiplexing) communication system, an optical module, an optical transmitter, a WDM optical transmission apparatus, and a method of controlling a wavelength of an optical module.
In the field of dense WDM, it is generally required that the optical signals are stable in wavelength for a long time period. Consequently, there have conventionally been developed techniques of providing the function of a wavelength monitor in an optical module.
The present invention provides a method of controlling a wavelength of a semiconductor laser for controlling an optical module that includes:
a light-emitting device that outputs laser light, a temperature detection unit that detects a temperature of the light-emitting device;
a wavelength monitor unit that monitors a wavelength of the laser light outputted from the light-emitting device and having passed through an optical filter; and
a wavelength adjustment unit that adjusts the wavelength of the laser light outputted from the light-emitting device based on a signal outputted form the wavelength monitor unit,
wherein a signal from the temperature detection unit is used to correct wavelength shift caused by a temperature characteristic of the optical filter by estimating a temperature of the optical filter.
The present invention provides an optical transmitter comprising:
an optical module including a light-emitting device that outputs laser light, a temperature detection unit that detects a temperature of the light-emitting device, a wavelength monitor unit that monitors a wavelength of the laser light outputted from the light-emitting device and having passed through an optical filter, and a wavelength adjustment unit that adjusts the wavelength of the laser light outputted from the light-emitting device based on a signal outputted form the wavelength monitor unit, the optical module being used to correct wavelength shift caused by a temperature characteristic of the optical filter by estimating a temperature of the optical filter using a signal from the temperature detection unit;
a control unit that fixes the lasing wavelength of the laser light outputted from the light-emitting device to a predetermined wavelength based on the signal outputted from the wavelength monitor unit; and
a correction unit that estimates the temperature of the optical filter based on the temperature of the light-emitting device detected by the temperature detection unit and outputs, to the control unit, a correction signal commanding the correction of the wavelength shift caused by the temperature characteristic of the optical filter based on the estimated temperature of the optical filter.
The present invention provides a WDM optical transmission apparatus comprising:
an optical module including a light-emitting device that outputs laser light, a temperature detection unit that detects a temperature of the light-emitting device, a wavelength monitor unit that monitors a wavelength of the laser light outputted from the light-emitting device and having passed through an optical filter, and a wavelength adjustment unit that adjusts the wavelength of the laser light outputted from the light-emitting device based on a signal outputted form the wavelength monitor unit, the optical module being used to correct wavelength shift caused by a temperature characteristic of the optical filter by estimating a temperature of the optical filter using a signal from the temperature detection unit; and
a plurality of optical transmitters that each include a control unit that fixes the lasing wavelength of the laser light outputted from the light-emitting device to a predetermined wavelength based on the signal outputted from the wavelength monitor unit, and a correction unit that estimates the temperature of the optical filter based on the temperature of the light-emitting device detected by the temperature detection unit and outputs, to the control unit, a correction signal commanding the correction of the wavelength shift caused by the temperature characteristic of the optical filter based on the estimated temperature of the optical filter,
wherein optical signals outputted from the optical transmitters are wavelength-multiplexed and transmitted.
The first present invention provides an optical module comprising:
a light-emitting device that outputs laser light;
an optical filter through which laser light outputted from a light-emitting device passes;
a temperature control module that controls a temperature of the light-emitting device and the optical filter;
a light-receiving device that receives the laser light through the optical filter; and
a lasing wavelength control unit that performs control of a temperature of the light-emitting device based on detection results of the light-receiving device,
wherein the lasing wavelength control unit satisfies the following relation:
z=xcex94y(1xe2x88x92a/x)
xe2x80x83where x is a shift amount per unit temperature of a lasing wavelength in a light-emitting device,
xcex94y is a set lasing wavelength spacing in the lasing wavelength control unit,
z is a wavelength width per period of the wavelength-light transmittance curve of the optical filter, and
a is a shift amount per unit temperature of the wavelength-light transmittance characteristic of the optical filter.
The second present invention provides an optical module comprising:
an optical filter through which laser light outputted from a light-emitting device passes;
a temperature detection module that detects a temperature of the optical filter;
a light-receiving device that receives the laser light through the optical filter; and
a lasing wavelength control unit that performs control of a temperature of the light-emitting device based on detection results of the light-receiving device and the temperature detection module,
wherein the lasing wavelength control unit satisfies the following relation:
z=xcex94y(1xe2x88x92a/x)
xe2x80x83where x is a shift amount per unit temperature of a lasing wavelength in a light-emitting device,
xcex94y is a set lasing wavelength spacing in the lasing wavelength control unit,
z is a wavelength width per period of the wavelength-light transmittance curve of the optical filter, and
a is a shift amount per unit temperature of the wavelength-light transmittance characteristic of the optical filter.
The present invention provides a method of controlling a wavelength of an optical module, comprising the steps of:
(a) generating a waveform with periodicity by having laser light outputted from a light-emitting device pass through an optical filter;
(b) detecting light intensity by causing laser light outgoing from the optical filter to enter a light-receiving device; and
(c) detecting a change of lasing wavelength of the laser light outputted from the light-emitting device using a detection result of the light-receiving device and performing control of a temperature of the light-emitting device using a lasing wavelength control unit with reference to a result of the lasing wavelength change detection so as to satisfy the following relation:
z=xcex94y(1xe2x88x92a/x)
xe2x80x83where x is a shift amount per unit temperature of a lasing wavelength in the light-emitting device,
xcex94y is a set lasing wavelength spacing in the lasing wavelength control unit,
z is a wavelength width per period of the wavelength-light transmittance curve of the optical filter, and
a is a shift amount per unit temperature of the wavelength-light transmittance characteristic of the optical filter.